Process for treating mineral oils



refining of lubricating oils.

Patented Feb. 6, 1940 Urwrrao STATES PATENT oer-Ice PROCESS FOR TREATINGMINERAL OILS Merrell R. Fenske and Wilbert B. McCluer, State College,Pa., assignors to Pennsylvania Petroleum ltesearch PennsylvaniaCorporation, a corporation of 4 Claims.

fining of petroleum oils and particularly tothe The invention pertainsmore particularly to the removal from lubricating oils, for instance,

from oils of Pennsylvania grade, of undesirable substances such ascolor, Conradson carbon, wax and/or components of lower. lubricatingvalue.

As pointed out in our copending application, Serial No. 731,778, we havediscovered that when a petroleum oil, and more particularly alubricating oil, for instance, one of Pennsylvania grade, isfractionated by means of solvents, that is, separated into fractionswhich do not differ very materially in viscosity index, the color,Conradson carbon and/or wax or among the less soluble components and,therefore, concentrate in the undissolved portion of the oil.

We have also discovered in the solvent extraction of lubricating oil andparticularly lubricating oil of Pennsylvania grade, to divide the oilintofractions respectively higher and lower in viscosity index, thatsmaller losses (of oil as extract) will occur if a given oil is dividedinto two or more cuts (differing chiefly as to molecular size orviscosity) prior to extraction than will occur if the overall oil isdirectly extracted. In other words, welhave found that smallerquantities of extract need be separated from an oil to bring said oil upto a given viscosity index if cuts of said oil are separately extractedand the various raflinates are combined. Furthermore,"the total quantityof extract decreases with the number ofcuts, making it desirable fromthe standpoint of economy in oil to extract relatively narrow cuts.

The fractionation of the oil for the purpose of obtaining narrow cutsthereof maybe accomplished by either fractional distillation or solventfractionation.

For the purposes of this application the term extraction when used inconnection with the separation of an oil into two or more parts willindicate that such separation is primarily for the purpose of producingoil fractions differing chiefly in viscosity index; that is, as tomolecular type; the term fractionation will be used to indicate thatsuch separation is primarily for the purpose of producing cuts differingchiefly in viscosity; that is, as to molecular size; the terms extractand raflinate will be used to indicate extraction products, and the termcut will be used to indicate a fractionation product.

As pointed out in said copendingapplication, a monohydric aliphaticalcohol having more than four carbon atoms, such'as secondary butylalcohol, tertiary butyl alcohol, normal amyl alcohol,

I isoamyl alcohol, secondary amyl alcohol and secondary butyl carbinol,may be added to a petroleum oil and more particularly a lubricating oil,such as one of Pennsylvania grade, under (Cl. 196-133) This inventionpertains generally to the reconditions conducive to the formation of twophases, and upon separationof the phases, it

will be found that the oil in each .phase will differ primarily as toviscosity and will not differ very materially in viscosity index. Thecolor and Conradson' carbon will concentrate in the undissolvedoilphase. The data also show that wax will tend to concentrate in theundissolved oil phase. 'In other words, the undissolved cut will containa higher percentage of color, Conradson carbon and/or wax than thedissolved cut. Thus, the dissolved cut will be in a higher state ofrefinement.

In the practice of this invention we now sub ject the undissolved cut tosolvent extraction with any solvent or solvents suitable for thispurpose and more particularly one which exhibits a high preferentialsolvent capacity for color and Conra'dson' carbon.

Any process and/or apparatus known in the art maybe employed forcarrying out this step, as well as the previous step of fractionation.

Because of the relativelyhigh concentration of color and Conraclsoncarbon in the undissolved cut, when this cut is subjected to solventextraction, relatively larger quantities of these undesirable componentsand relatively smaller quan-- titles of desired oil components will gointo the extractQ Therefore, losses in desirable oil components may bevery materially reduced.

It should be kept in mind that the undissolved cut is alfractio'n ofthe'overall oil, and that when this'jcut' is subjected to extraction,rather than the overall oil, savings are made in desirable oilcomponents by virtue of this fact alone and in addition to the savingsreferred to in the previous paragraph.

The undissolved cut may have any desired boiling range. The boilingrange will be determined bythe amount of oil in'the' dissolved oilphase. If a relatively large quantity of oil is dissolved it will beobvious that the undissolved cut will have a narrower boiling range thanit would have if smaller quantities of oil were dis solved.

Any other out or cuts may also be subjected to solvent extraction ifdesired. These cuts may be made by any means known in the art, forinstance, by fractionally precipitating a quantity or quantities of oilfrom the dissolved oil phase. I

solvent extraction, if desired, with or Without (but preferably with)the prior removal of fractionating solvent therefrom.

The concentration of color and Conradson carev bon in the heavier cut;or cuts will greatlyreduce the degree of or entirely eliminateextraction of the lighter cut or cuts according to requirements.

Solvents adapted for extraction purposes are acetaldehyde, acetone,acrolein, allyl alcohol, allyl isothiocyanate, aniline, aniline oil,benzaldehyde, benzonitrile, beta beta dichlorethyl ether, butylcarbitol, cellosolve acetate, cresol, cresylic acid, crotonaldehyde,estersol, ethyl acetate, ethyl alcohol, ethylene chlorohydrin, furfural,furfuryl alcohol, isopropyl alcohol, liquid sulfur dioxide, methylacetate, methyl alcohol, methyl cellosolve, methyl thiocyanate, mixedtoluidines, mononitronaphthalene, nitrobenzene, nitrotoluene,orthotoluidine, phenol phenyl acetate, phenyl thiocyanate, polyhydricalcohols, propionaldehyde, pyridine, tetrahydrofurfuryl alcohol,tolualdehyde, tolyl formate, tricresyl phosphate, xylidine, etc.

The higher concentration of wax in the heavier cut or cuts produced bythe solvent fractionation above referred to is, as a rule, not disturbedby solvent extraction of the cut or cuts with a solvent which isselective as to naphthenic constituents. This cut or cuts afterextraction may be subjected to any suitable dewaxing process known inthe art and because of the high concentration of wax in this cut or cutshigher percentage amounts of wax may be removed than would be possibleif the wax were not concentrated in said cut or cuts.

This makes it possible to either greatly reduce the degree of orentirely dispense with the dewaxing of the lighter cut or cuts accordingto requirements.

From the foregoing, it will be seen that a petroleum oil, and moreparticularly a lubricating oil of Pennsylvania grade, may be dividedinto any desired number of cuts; that the heavier cuts will have ahigher concentration of color, Conradson carbon and/or wax if the cutsare made by solvent fractionation; that a higher percentage amount ofcolor, Conradson carbon and/or wax may be removed with the same effortif the heavier cuts are treated rather than the overall oil; and thatsmaller losses of desirable lubricating components will occur if cuts ofan overall oil are separately extracted.

The term solvent in its broader phases includes any compound orplurality of compounds Whether in the vapor, liquid or solid phase.

In the claims the term lubricating oil when referred to is intended tomean an oil of a viscous character that is of the order of 35 Sayboltseconds at 210 F. or above.

This invention is particularly useful in the refining of lubricatingoils of Pennsylvania grade. For instance, it is found to be much moreeconomical in losses of oil as extract to separately extract waxdistillate and cylinder stock or viscous neutral and bright stock thanit is to extract a long residuum or a mixture of wax distillate andcylinder stock or a mixture of viscous neutral and bright stock.

Furthermore, it is found economical and expedient to first separate along residuum by solvent fractionation into cuts corresponding to waxdistillate and cylinder stock or viscous neutral and bright stock, asthe case might be, for, by the use of solvent fractionation, color,Conradson carbon and/or Wax is concentrated in the cylinder stock orbright stock cuts which, in many cases, may alone be subjected tosolvent extraction and/or dewaxing, since the materials to be removedare concentrated therein. In any case, the lighter fractions requiremuch less treatment, in view of the refining effected by the solventfractionation step.

Moreover, the solvent fractionation step makes available for the firsttime the separate extraction of cuts of cylinder stock and bright stocksince the latter stocks are ordinarily not separable by distillationwithout undue decomposition.

In the claims the term Pennsylvania grade residuum oil is intended tomean a residuum resulting from the distillation of a Pennsylvania gradecrude oil, or of a fraction thereof containing relatively heavycomponents, or a Pennsylvania oil fraction of comparable viscosityobtained by solvent fractionation or any other fractionating means, or aproduct of such residuum other than a distillate thereof, and isemployed generically to include a mixture of such re-' siduums.

While the invention has been particularly described, it is to beunderstood that this is by Way of illustration and that changes,omissions, additions, substitutions and/or modifications may be madewithout departing from the spirit of the invention which is intended tobe limited only as required by the prior art.

We claim:

1. A process comprising separating wax containing lubricating oil intotwo fractions by means of solvent fractionation with a solvent selectivechiefly as to molecular size to concentrate substances such as color,Conradson carbon and wax in the less soluble of said fractions,subjecting the less soluble of said fractions to olvent extraction witha solvent selective chiefly as to molecular type, dewaxing the rafiinatethus produced, segregating the extract and wax thus obtained, andcombining the remainder of said oil.

2. A process comprising separating wax containing lubricating oil intotwo fractions by means of solvent fractionation with a solventcomprising a monohydric aliphatic alcohol having at least four carbonatoms to concentrate color, Conradson carbon and wax in the less solubleof said fractions, subjecting the less soluble of said fractions tosolvent extraction with a solvent selective chiefly as to moleculartype, dewaxing the raffinate thus produced, segregating the extract andwax thus obtained, and combining the remainder of said oil.

3. A process comprising separating wax containing lubricating oil intotwo fractions by means of solvent fractionation with a solvent selectivechiefly as to molecular size to concentrate wax in the less soluble ofsaid fractions, subjecting the less soluble of said fractions toclewaxing, segregating the wax thus obtained, and combining theremainder of said oil.

4. A process comprising separating wax containing lubricating oil intotwo fractions by means of solvent fractionation with a solventcomprising a monohydric aliphatic alcohol having at least four carbonatoms to concentrate wax in the less soluble of said fractions,subjecting the less soluble of said fractions to dewaxing, segregatingthe wax thus obtained, and combining the remainder of said oil.

MERRELL R. FENSKE. WILBERT B. MCCLUER.

